Prior art devices for sealing a rotating shaft are disclosed in U.S. Pat. Nos. 4,022,479 (Orlowski) and 5,024,451 (Borowski). Seal devices of this type may be used to inhibit oil from escaping out of a bearing housing and/or to inhibit contaminants from working their way into the housing. The prior art devices are formed of at least two ring-shaped members that rotate with respect to each other when the shaft is rotated. One of the members is fixed to the housing and does not rotate. The other member rotates with the rotating shaft.
The two ring members should be located very close together, particularly when the seal device is used to isolate the bearing from small particulate contaminants. Even small quantities of such contaminants are capable of significantly deteriorating the bearing. To prevent such contamination, the two relatively rotatable ring members must be held together very closely, with only a very narrow space therebetween.
The ring members of the Orlowski seal device are connected together by a separate securing apparatus, not shown in the prior art patent. The ring members themselves have no structure for establishing and maintaining a narrow spacing therebetween. Therefore, the prior art seal device cannot be manufactured as a unit with a preset, fixed spacing. The spacing between the ring members has to be set when the seal device is installed into the housing. This leaves room for human error outside the control of the device manufacturer. In particular, the Orlowski device can be improperly installed, with the ring members located too far apart to perform satisfactorily. Another problem with the Orlowski device is that the ring members may be separated subsequent to installation, for example by high pressure cleaning spray.
The ring members of the Borowski device are held together by a bead and a groove provided on the ring members themselves. The bead fits within the groove with an interference fit. This arrangement is an improvement over the Orlowski system in the sense that no separate securing apparatus is needed. But the Borowski device is still unsatisfactory because the bead must be resiliently deformed to be positioned within the groove, and the groove must be correspondingly enlarged to receive the deformed bead. The deformation of the bead during assembly makes it difficult to achieve the desired close positioning between the two ring members, as explained in more detail below.
Labyrinth seals may be used in applications which make it time consuming and difficult to either install the seal or to replace an existing seal. Further, labyrinth seals are sometimes used in applications in which it is not only time consuming to install a seal, but also in which the downtime of the equipment is costly. For example, in an aluminum mill, unplanned downtime to replace a labyrinth seal can be very expensive. It is, thus, desirable to utilize in such applications seals which are relatively easy to replace in a timely fashion.
Prior art devices showing split seals are disclosed in U.S. Pat. Nos. 4,863,177 (Rockwood et al.), 4,576,384 (Azibert), 4,575,098 (Escue), and 2,141,102 (Brooke). The device referred to in Rockwood et al. is a labyrinth seal having a split rotor and stator. The rotor halves integrally interlock together through a hook and protrusion arrangement, while the stator halves fit closely together as a mortis and tenon and are stable in relation to each due to the close fits. The device of Rockwood et al. has no rotor which interlocks with a stator.
The device referred to in Azibert is a split mechanical face seal having a rotary split seal ring assembly and a stationary split seal ring assembly. The seal ring assemblies are not arranged to create a labyrinth seal and they are not interlocked with each other.
The device referred to in Escue, like Azibert, is a split seal having a rotary seal means and a stationary seal means. The rotary seal means and a stationary seal means are split, but they are not arranged to create a labyrinth seal and they are not interlocked with each other.
The device referred to in Brooke is a labyrinth protective device including a stationary lug and a rotating mount which rotates on a ball or roller bearing. The device of Brooke, however, does not include a rotor mounted on a rotating shaft. Further, it has no mechanism for returning potentially harmful contaminants to the outside of the seal and has no mechanism for returning oil which has entered the seal back to the oil reservoir in the housing.